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Author Topic: Car geeks, lend me your wrenches!
MacManKrisK

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Icon 1 posted July 23, 2009 15:58      Profile for MacManKrisK     Send New Private Message       Edit/Delete Post   Reply With Quote 
VW woes, I know this isn't a VW forum, but it seems like a general mechanical issue. I'll give you the condensed version.

1978 VW Type II ("Bus, Transporter, Fukinwagen, etc.") 1971cc (called 2L) "Type IV" engine with Bosch "L-Jetronic" air-flow-control electronic fuel injection.

I pulled out the engine to replace the clutch and have the flywheel resurfaced. Put the engine back in and got it running pretty well. Fixed the cold idle issue ('twas a leaky EGR valve).

The problem is: I start it, it fires up, idles well, runs well. Then it gets warmed up (not overheating.. just up to general operating temp) and *pfft* dies. Dead as a doorknob. It won't restart until it cools down some, usually 5 minutes. If you let it cool down more it'll run longer before dying, but it doesn't need to cool down *much* to be able to start again.

Here's what I've done so far:
  • Compression Check: OK (110-115 lbs)
  • Checked resistance of cap, rotor, plug wires, coil wire, etc.: all within tolerance
  • Checked spark at coil: Nothing to write home about but acceptable
  • Checked spark at plugs: same as coil.. not *great* but pretty good
  • Replaced Coil (just in case): no difference in spark color
  • Checked points: points are shiny and clean, not shorted, opening appropriately
  • Checked vacuum: about 15lbs. (Hg) at idle, 20-25lbs. when revved... good for this engine

The Fuel Injection seems to be working fine. If I keep cranking when it won't start you can smell the gas that's being injected (but not burned). Also, I tried to run it on starting fluid (I know, bad idea) and it won't even do that. Once it cools off a bit, it starts right back up.

I am *out* of ideas... anyone have any?

--------------------
"Buy low, sell high
get rich and you still die"


Posts: 2331 | From: Southwest Michigan, USA | Registered: Oct 2001  |  IP: Logged
TheMoMan
BlabberMouth, a Blabber Odyssey
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Icon 1 posted July 24, 2009 02:48      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
_________________ MacManKrisK

____ The two things I would check first is the Points Condenser you may have one that is in hot failure mode. Second and I am not sure if VW used a ballast resister in the coil circuit, they have been known to go open on heat.

____ If it is an electrical heat issue just leaving the key on with the points closed should cause the errant part to fail with out the engine running. Engine running a voltmeter reading at the coil while waiting for it to quit would be informative. Especially if it changed when in failure mode.

--------------------
Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.


Benjamin Franklin,

Posts: 5835 | From: Just South of the Huron National Forest, in the water shed of the Rifle River | Registered: Sep 2002  |  IP: Logged
CommanderShroom
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Icon 1 posted July 24, 2009 06:30      Profile for CommanderShroom     Send New Private Message       Edit/Delete Post   Reply With Quote 
You got fuel, do you know if you have fire?

Run it til it quits, pop a plug or, if the car is too hot, a plug wire and see if you have a breakdown in the spark.

I am guessing that its the condenser also. But also double check that coil, I have gotten garbage right out of the box before.

Posts: 2463 | From: Utarrrrggggghhh!!!!!!!! | Registered: Mar 2003  |  IP: Logged
MacManKrisK

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Icon 1 posted July 24, 2009 09:34      Profile for MacManKrisK     Send New Private Message       Edit/Delete Post   Reply With Quote 
I have spark, I've already checked it. Sparks when cold, sparks when hot. They're not superbly bright and blue, but they are more than adequate. There's no difference in spark color hot or cold. And, FWIW, the coil was the first thing I suspected.

I have a "warm up valve" (more properly known as the "Aux. Air Regulator" or "Aux. Air Bypass") that I just installed and I'm going to remove it and put my old one back in and see if that changes anything. If I get no joy from that, I'll throw in my spare condenser. Honestly, though, it *should* run with a bad condenser.. it has before.. it just runs very poorly...

--------------------
"Buy low, sell high
get rich and you still die"


Posts: 2331 | From: Southwest Michigan, USA | Registered: Oct 2001  |  IP: Logged
CommanderShroom
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Icon 1 posted July 24, 2009 10:25      Profile for CommanderShroom     Send New Private Message       Edit/Delete Post   Reply With Quote 
If you are getting fire, it keeps me from totally thinking it is the ignition, but not completely.
Now you said you had just done the EGR and Clutch.

While you were in there, what else was done?

Also what did you have to pull that was injector related?

Since you mentioned changing other parts, is there a possibility that you got close to other essential wiring?

It could be as stupid as a loose connector in an area you thought wasn't messed with.

I know that earlier Jetronics were more or less mechanical injection. Does yours have the flap door in the air breather that meters the fuel? I had an older Scirroco that was a bit long in the tooth and blow-by would gum up the works and creates poor idle issues and suck. A bit of carb cleaner to clear out the oil and it would be great for a few more months.

What about wires plugs cap and rotor? Are they in good shape? Old or new? Have you pulled the plugs to look for discoloration? I have seen situations where weak spark would fail under full engine load. So you would have a spark, just not enough to keep it running.

It comes down to compression fire and fuel. So if you aren't losing compression once warmed up, you are left with fire and fuel. I would start prowling out things that are different from before you pulled the motor and work from there.

Posts: 2463 | From: Utarrrrggggghhh!!!!!!!! | Registered: Mar 2003  |  IP: Logged
TheMoMan
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Icon 1 posted July 24, 2009 10:47      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
_____________________ Hey ____________________

____ I'm with shroom on many of his points, it was either giving you trouble before the clutch job or you have caused it. Check grounds engine to body, chassis to body, is the distributer tight and is it grounded. Inside the dist. is the advance plate grounded? Is that little plastic insulator for the points to coil wire in good shape?

--------------------
Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.


Benjamin Franklin,

Posts: 5835 | From: Just South of the Huron National Forest, in the water shed of the Rifle River | Registered: Sep 2002  |  IP: Logged
MacManKrisK

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Icon 1 posted July 24, 2009 10:50      Profile for MacManKrisK     Send New Private Message       Edit/Delete Post   Reply With Quote 
Shroom: all good ideas, thanks.

The EGR I just blocked off because it was leaking (and there hasn't been a proper EGR connection attached to this engine for as long as I've owned it). I replaced the Aux Air Regulator (a valve that is parallel to the throttle body and allows more *metered* air in to enrich the mixture during warm up) while I was in there. That required disconnecting the fuel rail at the cold start injector to make room for hands and tools to reach. I have since swapped the "newsed" one back for the original, to no avail.

I should check Temp Sensor #2 (cylinder head temp) and make sure it's properly grounding....

I have the flappy door "mass air flow" box, it appears to be working blissfully well.

I'm 99% sure (which is as sure as I can realistically be) that the ignition system is good. My most recent tests indicate that I may be losing vacuum.. but I have no idea where.

Fuel pressure is about 32psi... which is pretty damn close to the 35psi specification. I'm not going to sneeze at that one.

--------------------
"Buy low, sell high
get rich and you still die"


Posts: 2331 | From: Southwest Michigan, USA | Registered: Oct 2001  |  IP: Logged
TheMoMan
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Icon 1 posted July 24, 2009 10:56      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
__________________ MMKK ______________________

___ Please check valve lash, it could be too tight, that would hold the valves open at higher temps.

--------------------
Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.


Benjamin Franklin,

Posts: 5835 | From: Just South of the Huron National Forest, in the water shed of the Rifle River | Registered: Sep 2002  |  IP: Logged
GrumpySteen

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Icon 10 posted July 24, 2009 11:08      Profile for GrumpySteen     Send New Private Message       Edit/Delete Post   Reply With Quote 
The solution is simple: Get a Macintosh!

Wait, what?

--------------------
Worst. Celibate. Ever.

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CommanderShroom
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Icon 1 posted July 24, 2009 13:54      Profile for CommanderShroom     Send New Private Message       Edit/Delete Post   Reply With Quote 
Correct me if I am wrong. Doesn't the Jetronic also have a cold start fuel valve that enriches the mixture when the motor is cold?

It may be possible that if you do have a vacuum leak, that when the extra fuel is cut off, it is creating too lean of a mixture to run. I remember that some of the earlier versions of that fuel injection had a way to adjust the fuel ratio from the box. Don't know if yours has such a provision. And there were a few later versions that had a similar setup off the air meter flap that did the same thing before they went to a fully looped system.

See if you can trace any areas of possible vacuum leaks, a can of starting fluid or WD-40 will be helpful here. That will at least rule out a possible lean condition from a vacuum leak. I would check at the manifolds to the heads, and all your intake hoses, and then go onto checking vacuum lines.

Good luck.

--------------------
Does he know our big secret?
Has one of us confessed?
'Bout the wires circuits and motors
Buried in our chest

Posts: 2463 | From: Utarrrrggggghhh!!!!!!!! | Registered: Mar 2003  |  IP: Logged
MacManKrisK

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Icon 1 posted July 24, 2009 16:33      Profile for MacManKrisK     Send New Private Message       Edit/Delete Post   Reply With Quote 
"it's usually something simple"

The fuel injection is powered by a "double-relay", part of which controls the pump and the rest of which controls providing power to the entire rest of the system. Power comes to the coil from the key (a single frakking wire runs from the switch to the coil and it powers *EVERYTHING* in the engine compartment). A second connector on the positive terminal on the coil signals the double-relay to close, thus energizing the fuel injection system.

All the power for the entire system (except the fuel pump): injectors, computer, sensors, etc. comes from terminal 88y on the relay. Terminal 88y had a loose wire... it would warm up and then loosen up just enough when it got warm and kill the fuel injection and the engine would sputter to a stop. Let it cool down and it'd tighten up a bit and run again.

3 days on a loose wire.. but at the same time, I'm glad it's fixed!

--------------------
"Buy low, sell high
get rich and you still die"


Posts: 2331 | From: Southwest Michigan, USA | Registered: Oct 2001  |  IP: Logged
TheMoMan
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Icon 1 posted July 24, 2009 17:29      Profile for TheMoMan         Edit/Delete Post   Reply With Quote 
______________________ MacManKrisK ______________________

____ On some cars that relay is also tied to the low oil pressure light, so if oil pressure falls the pump stops, You could restart the car because of a bypass relay but when you released the key it would stop, took me a while to learn that one.

--------------------
Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety.


Benjamin Franklin,

Posts: 5835 | From: Just South of the Huron National Forest, in the water shed of the Rifle River | Registered: Sep 2002  |  IP: Logged
MacManKrisK

Gold Hearted SuperFan!
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Member Rated:
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Icon 1 posted July 24, 2009 22:56      Profile for MacManKrisK     Send New Private Message       Edit/Delete Post   Reply With Quote 
MoMan: aye.. on this particular beast the oil pressure sensor is connected only to the light on the dashboard. In a similar fashion, however, the pump only turns on when there is air going through the Mass Air Flow sensor, as soon as the veins close the pump shuts off.

--------------------
"Buy low, sell high
get rich and you still die"


Posts: 2331 | From: Southwest Michigan, USA | Registered: Oct 2001  |  IP: Logged


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